Felryite is a pale gemstone that can trap souls. Souls can be used as a powerful energy source. They can be used to extend the lifespan of a person by 100 years, to create a sentient AI and an über-powerful computing systems.
Only healthy souls can be used safely. Using corrupted and evil souls is very dangerous and the only use for evil souls is for weapon systems like hunter-killer drones and homing ammunition.
How much money would a soul cost?
Felryite is as rare as diamonds.
PS : Detecting corrupted or pure souls is easy. For example the souls of psychopaths and criminals are evil souls, while the souls of philanthropist people, who do good deeds, are pure. The souls of babies are pure too. Felryite works like a magnet, meaning anyone can trap souls with a chunk of Felryite.